A FOUR-YEAR-OLD white rhinoceros has been killed after poachers broke into Thoiry Zoo in France, to hack off his horn.

The animal, named Vince, was found dead by keepers in the zoo's African enclosure on Tuesday morning. He had been shot in the head three times and his large horn had been removed - most likely by a chainsaw.

Vince's second horn was only partially cut. Police said either the attackers were disturbed or their equipment failed.

Two other rhinos who shared the enclosure with Vince, a 27-year-old female and five-year-old male, escaped the massacre unharmed.

Vince was brought to Thoiry in March 2015. He was born in captivity in the Netherlands in 2012.

The perpetrators forced the main gate and managed to break through at least two other security barriers on Monday night. All without disturbing five people who reside in the grounds.

Although the zoo is fitted with video surveillance, cameras were not installed near the rhinos' exhibit.

The brazen attack is the first of its kind in Europe.

Thierry Duguet, the manager of the zoo, told AFP: "This has never happened before in a zoo, either in France or in Europe.

Zoo staff have understandably been left traumatised by the attack.

"We are extremely shocked and upset - this is supposed to be a sanctuary for the animals," Duguet said.

Colomba de Panouse, part of the family which set up the zoo, told AFP: "The rhinos' warden, Elodie, is very distressed by what's happened.

"She was the one who made this macabre discovery and now she can't talk" because of the shock.

Investigators have placed the horn's worth between $31,700-$42,250.

Rhino horn is highly sought after in Asia for its use in traditional medicine and as an aphrodisiac. Principle demand comes from China and Vietnam.

On the black market rhino horn sells for up to $60,000 per kilogram. To put things into perspective that is more than gold or cocaine.

The poaching of rhinos has proceeded at alarming rates. Three of the world's five species of rhino are "critically endangered."

In the past eight years alone, roughly a quarter of the world's rhino population has been killed in South Africa, which is home to 80 per cent of the remaining animals.

It's not all grim news though. The two African species the white rhino and the black rhino, considered near threatened and critically endangered respectively, have been the focus of conservation programs in recent years.

Indeed, the southern white rhino was once on the brink of extinction. However, intense conservation efforts, such as the breeding program in which Vince was apart of, has seen numbers climb to 20,000.

As long as zoos remain safe havens, and this attack a brutal one-off, these creatures still have a fighting chance.